The present disclosure relates to thermal management as well as thermal runaway prevention. In particular, it relates to active thermal management and thermal runaway prevention for high energy density lithium ion battery packs.
Lithium ion battery cells and battery packs have two primary concerns with respect to thermal management that must be addressed in order to ensure safety and long life. The first concern is that the individual battery cells must be maintained within their specified temperature range, and cell-to-cell temperature differences inside of the battery packs must be maintained in order to ensure long life and to maximize the battery pack value. The second concern is that faulty, damaged, or abused cells may enter thermal runaway (especially at elevated temperatures), thereby leading to compromised cells and battery, in a way typically not controlled for battery designs.
Currently, various schemes exist for cooling batteries that use liquids confined to pipes, tubes, or other channels where some portion of the individual battery cells are in contact with the fluid channel or have a path to reject heat to the channel, either through contact with a thermally conductive component (e.g., a heat spreader) or through direct contact with other battery cells. These methods typically have limited contact area with individual battery cells, have poor thermal conduction across the contact area, and may have several components through which heat from the battery cell must travel to reach the ultimate cooling fluid, thereby resulting in the limited ability to effectively remove heat. These measures introduce significant additional mass and volume to the battery pack that reduce the volume, weight, and effectiveness of the battery pack while increasing cost and frequently without providing significant protection from thermal runaway events.
Another existing solution is to embed individual battery cells into a solid material that changes phase at an elevated temperature, thus removing large quantities of heat in the process of melting without a corresponding increase in temperature above the melting point. While potentially beneficial in preventing thermal runaway from an individual cell, these solutions are either passive and allow heat in excess of that removed by convection from the case to accumulate up to the melting point of the phase change material, or require additional tubes and/or pipes to implement a traditional active management solution that add their associated weight and volume to the weight, volume, and cost of the phase change material itself. In either case, the possibility exists that the phase change material may already be in its molten state at the onset of thermal runaway, and therefore may not be able to provide any ability to protect against an undesired thermal event. Additionally, the manufacture of the bulk phase change material embedded in a binder matrix and the machining of the resulting bulk material into an appropriate shape for this application adds to the overall cost of the system.
Therefore, an improved system and method for thermal management and thermal runaway prevention for battery cells is needed.